Camera with partial exposed frame film detector and battery monitor

ABSTRACT

A camera which determines whether a film cartridge loaded in the camera is a partial cartridge, containing photographic film having an exposed frame and an unexposed frame, or not, and feeds the photographic film from the loaded film cartridge up to a first unexposed frame if determining that the loaded film cartridge is a partial cartridge, the camera includes a first battery checking unit defined by a first determination means for determining whether voltage of a battery in the camera is more than a first threshold level, and first prohibiting means for prohibiting photographing if the loaded film cartridge is not determined as being the partial cartridge and determining, the first determination means determines that the voltage of the battery is less than the first threshold level. The camera also including a second battery checking unit defined by a second determination means for determining whether the voltage of the battery is more than a second threshold level, which is higher than the first threshold level, and second prohibiting means for prohibiting photographing if the loaded film cartridge is determined as being the partial cartridge and the second determination means determines that the voltage of the battery is less than the second threshold.

This is a divisional of Application Ser. No. 08/940,776 filed Sep. 30,1997, now U.S. Pat. No. 6,026,249, the disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a magnetic recording andregenerating unit for photographic film and a camera, and moreparticularly to a magnetic recording and regenerating unit which recordsmagnetic information in a magnetic recording layer on the photographicfilm and regenerates the magnetic information recorded in the magneticrecording layer, and a camera which the magnetic recording andregenerating unit applies to.

2. Description of Related Art

Advanced photographic film has been proposed in which one side of silversalt film is coated with a magnetic layer (U.S. Pat. No. 5,130,745). Afilm cartridge which contains the film and a camera which uses the filmcartridge for photographing have also been proposed, and they arestandardized worldwide.

As shown in FIGS. 32 (a) and (b), an advanced cartridge roll film 100 isconstructed in such a manner that the film 103 which is wound around aspool 102 is stored in a cartridge case 101, which is substantiallycylindrical. A light-shielding lid 104 is provided at one end of thecartridge case 101. The film 103 is completely stored in the cartridgecase 101 when the roll film 100 has not loaded in the camera or afterthe roll film 100 has been taken out from the camera, and thelight-shielding lid 104 protects the film 103 from external light.

A data disk 105 is provided at a side end of the cartridge case 101, andthe data disk 105 rotates in association with the spool 102. A bar codeis printed on the exterior face of the data disk 105, and the bar codeindicates the type and sensitivity of the film 103, the number of framesto be exposed, etc.

Apertures which are shaped like a circle, a square, a cross and asemicircle are formed on the other side end of the cartridge case 101. Asectorial white plate (not shown) is provided at the back of theseapertures, and the white plate rotates in association with the spool102. One of the circle, the square, the cross and the semicircle isdisplayed in white according to a position where the white plate stops.The display of the circle in white indicates that the film in thecartridge case 101 is unexposed; the display of the square in whiteindicates that the film has already been developed; the display of thecross indicates that the film has already been exposed but undeveloped;and the display of the semicircle in white indicates that the film hassome unexposed frames remaining. The display in white is called VEI(visual exposure index), and the index is seen with eyes from theoutside to confirm the status of the film used.

The film 103 is constructed in such a way that a surface 103F of thefilm base is coated with a silver salt photosensitive layer and thereverse side 103R of the film is coated with a magnetic recording layer.Multiple perforations 121 are formed at the edge of the film 103 tospecify the range of each frame 120. The photographing information suchas the type of a light source for photographing and a focal length, andthe information such as the title of the photograph used as a message toa user can be magnetically recorded in magnetic record areas 124, 125 atthe upper and lower end of each frame.

When the cartridge film is loaded in the camera, an optical readingmechanism in the camera reads information indicated with the bar code onthe data disk 105, and detects the position of the white plate, therebyautomatically recognizing the information relating to the film and theused status of the film. In the case of the cartridge film with noexposed film or with some unexposed frame remaining, the light-shieldinglid 104 is opened and the spool 102 is rotated in a predetermineddirection, so that the film 103 can feed to the first unexposed frame.

After all frames on the film 103 are exposed, a rewind mechanism in thecamera takes up the film 103 into the cartridge case 101, and closes thelight-shielding lid 104. Further, the white plate, which is fixed on thespool 102, is stopped in a manner to face the cross-shaped aperture,thereby displaying the cross in white to indicate that the film hasalready been exposed.

If the film is forcibly rewound during photographing with some unexposedframes remaining, the rewind mechanism in the camera takes up the film103 into the cartridge case 101, and closes the light-shielding lid 104.Further, the white plate, which is fixed on the spool 102, is stopped ina manner to face the semicircular aperture, thereby displaying thesemicircle in white to indicate that the film has some unexposed framesremaining.

On the other hand, if the loaded cartridge contains the film on whichall frames are exposed or developed, the process is executed to preventthe automatic feeding or the like because photographing is impossible.

According to the above-described camera, the film may be forciblyrewound in a state where there are some unexposed frames remaining onthe film, and the film cartridge may be taken out of the camera(hereinafter this film cartridge, which contains the film beingpartially exposed, is referred to as "a partial cartridge"). When thepartial cartridge, which contains the photographic film with one or moreof exposed frames and one or more of unexposed frames, is loaded againin the camera, the information in the magnetic recording layer is readvia a magnetic head in the camera, and the film feeds to an area with nomagnetic information recorded. Thereby, the photographing can beperformed from an unexposed frame.

The magnetic recording layer formed on the photographic film has a lowmagnetic density. Moreover, the base thereof is harder than aconventional magnetic tape, and thus a head touch easily becomesunstable. Hence, a special magnetic head only for reading is provided inwhich the number of turns of the coil is increased so as to exactly readthe information.

In a magnetic head (a regenerating head) in a conventional magneticregenerating unit for a camera, which regenerates the magneticinformation from the magnetic recording layer on the photographic film,the number of turns of the coil wound around the core is approximately1500. That is because S/N is lowered if the number of turns is small,and thus the magnetic information is difficult to read.

On the other hand, a magnetic head (a recording head) which records themagnetic information in the magnetic recording layer on the photographicfilm cannot be driven if the number of turns is large. For this reason,the number of turns of the coil is usually between 80 and 100. Thus, aregenerating head and a recording head are provided independently of oneanother, or a recording coil and a regenerating coil are wound around acore.

FIG. 33 illustrates an example of a conventional magnetic head driver.The magnetic head driver 150 is driven by electricity supplied from apower source V_(B), and a lithium battery, which is used as a powersource for the camera as a whole, is used as the power source V_(B). Amagnetic head 152 is driven by bridge-connected switching transistors154, 155, 156, 157, and ON/OFF of which are controlled by controltransistors 160, 161. The control transistors 160, 161 are turned on andoff, respectively, by switching signals (a clock pulse and a data pulse)which oppositely switch the first port P1 and the second port P2 onto ahigh (H) level and a low (L) level.

After the start of the magnetic recording, if the port P1 becomes the Llevel and the port P2 becomes the H level according to the clock pulseand the data pulse from a microcomputer, the control transistor 160 isturned off and the control transistor 161 is turned on. Thereby, theswitching transistors 154, 156 are turned off, and the switchingtransistors 155, 157 are turned on. Thus, the recording current I_(H)flows from the right to the left in the drawing through a coil 152a,which composes the magnetic head 152. Thereby, the magnetic head 152generates a magnetic field in which the magnetic flux turns in the filmfeed direction, and a magnetized area ("N magnetized area") in which themagnetic flux turns in the film feed direction is recorded in themagnetic recording layer. On the other hand, when the port P1 becomesthe H level and the port P2 becomes the L level, the control transistor160 is turned on and the control transistor 161 is turned off. Thereby,the switching transistors 154, 156 are turned on, and the switchingtransistors 155, 157 are turned off. The recording current flows throughthe coil 152a in the reverse direction, and the magnetic head 152generates a magnetic field such that the magnetic flux turns in adirection opposite to the film feed direction, and a magnetized area ("Smagnetized area") in which the magnetic flux is turns in the directionopposite to the film feed direction is recorded in the magneticrecording layer.

The above-described conventional magnetic recording and regeneratingunit, however, employs a sensitive and precise regenerating magnetichead in order to read the information recorded in the magnetic recordinglayer, and this magnetic head is large and expensive. Moreover, sincethe regenerating magnetic head is provided independently of therecording magnetic head, or the recording and regenerating head uses twocoils wound on a core for recording and regenerating, the magnetichead(s) is large and a driver circuit, etc. connected to the magnetichead has the complicated structure. For this reason, the cost isincreased, and the camera cannot be compact and lightweight. Since thenumber of turns of the coil is large, the magnetic head (theregenerating head) in the conventional magnetic regenerating unit forthe camera is large and expensive. Due to the difference in the numberof turns of the coil in the recording head and the regenerating head, itis impossible to combine them as one magnetic head.

Furthermore, the above-mentioned magnetic head reads the magneticinformation while the film is feeding, and thus the noise of the filmfeed motor easily overlaps with the information. In particular, sincethe recently-developed cameras are required to be compact, and the motoris arranged close to the magnetic head, the errors easily take place inthe process of reading the magnetic information.

If the conventional magnetic head driver is used as shown in FIG. 33,and when all the switching transistors 154, 155, 156, 157 are turned offon completion of recording the last "S magnetized area", a closedcircuit including the magnetic head 152 becomes unstable, and anoscillating current flows through the coil 152a due to the effects ofinductance and capacitance within the magnetic head driver. For thisreason, there is a problem in that the improper magnetic information isrecorded after recording of the last "S magnetized area" because of theoscillating current. To solve this problem, a method has been proposedin which all the transistors 154, 155, 156, 157 are turned on toshort-circuit the coil 152a after recording of the last magnetic data(Japanese Patent Application No. 7-128234). This method is effective ina magnetic head driver only for recording, which can have highresistance 164, 165, but is not suitable for a magnetic head driverwhich is used for both recording and regenerating and has to have smallresistance 164, 165 because of the small number of turns of the coil152a.

On the other hand, there are well known a four-terminal magnetic head inwhich the recording coil and the regenerating coil are wound on a core,a three-terminal magnetic head in which the regenerating coil includesthe recording coil, and the like. In the magnetic head which isconstructed in this manner, the number of turns of the regenerating coilis usually dozens of times as many as the recording coil. When therecording current flows through the recording coil with the drive powerof approximately 3 V, a induced current flows through the regeneratingcoil and a high induced voltage of several dozens V is generated betweenthe ends of the regenerating coil. If the high voltage is directlyapplied to the amplification circuit for regeneration, elementscomposing the amplification circuit such as an operational amplifier arebroken.

If a protection circuit is provided at the input stage of theamplification circuit for regeneration, or a switch, etc. forelectrically cutting off the regenerating amplification circuit from themagnetic head is provided in order to eliminate the above-describeddisadvantages, the great noise overlaps with the regenerated signal, andthe cost is increased.

Furthermore, if the partial cartridge is loaded in the camera, whether aframe is exposed or unexposed must be determined, and the photographicfilm must be fed to the first unexposed frame, thus requiring muchelectricity to prepare for photographing. In particular, if whether aframe is exposed or unexposed is determined according to the magneticinformation recorded in the magnetic recording layer on the photographicfilm, the photographic film must be fed at a proper speed. If, forexample, the film feed speed changes due to the exhaustion of thebattery in the camera, whether a frame is exposed or unexposed cannot bedetermined, and thus it is impossible to prepare for photographing ofthe partial cartridge.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a low-noise andlow-priced magnetic recording and regenerating unit for photographicfilm which uses a single magnetic head for both recording andregenerating consisting of a single coil wound around a single core, andwhich is able to use a recording circuit and a regenerating circuit inthe stable condition without effects of mutual noise, and which is ableto prevent the breaking of an operational amplifier of the amplificationcircuit during recording, and a camera which is provided with themagnetic recording and regenerating unit.

It is another object of the present invention to provide a compactcamera which is able to effectively eliminate the noise of a motor andcorrectly determine whether any magnetic information is recorded or notand feed the film to the position of an unexposed frame.

It is yet another object of the present invention to provide a magneticrecording and regenerating unit for photographic film which decreasesthe number of turns of a coil in a regenerating magnetic head so as tomake the magnetic head smaller and less expensive and read all thenecessary information, and which may be used as a magnetic head forrecording, and a camera which is provided with the magnetic recordingand regenerating unit.

To achieve the above-mentioned objects, a camera of the presentinvention which loads therein a film cartridge containing photographicfilm coated with a magnetic recording layer, has film feed means forfeeding the photographic film from the loaded film cartridge with amotor, determines whether the loaded film cartridge is a partialcartridge, containing a photographic film having an exposed frame and anunexposed frame, or not, and feeds the photographic film from the loadedfilm cartridge up to a first unexposed frame if determining that theloaded film cartridge is the partial cartridge; the camera comprises: amagnetic recording means for recording magnetic information in amagnetic record area on the magnetic recording layer corresponding to anexposed frame during one-frame feeding in every photographing; and amagnetic regenerating means being unexposed frame detecting means fordetecting the first unexposed frame according to whether magneticinformation is recorded in a magnetic record area for each frame on thephotographic film, if determining that the loaded film cartridge is thepartial cartridge, the magnetic regenerating means comprising a magnetichead for contacting the magnetic recording layer while the photographicfilm is feeding, the magnetic head including a coil wound on a core; anamplification circuit for amplifying signal voltage generated betweenterminals of the coil; a smoothing circuit for smoothing signals outputfrom the amplification circuit and outputting the smoothed signals; anda magnetic information detecting means for detecting whether anymagnetic information is recorded in the magnetic record area for eachframe on the photographic film by determining a voltage level of thesignals output from the smoothing circuit and comparing the determinedvoltage level with a reference level.

According to the present invention, the amplification circuit amplifiesthe signal voltage generated at ends of the coil in the magnetic head,and then the smoothing circuit smoothes the signal voltage. Then, thevoltage level of the smoothed signal is read so as to determine whetherany magnetic information is recorded or not. The signal is smoothedwithout accurately reproducing the information recorded in the magneticrecording layer from the signal obtained via the magnetic head, so thatthe number of turns of the coil in the magnetic head can be small, andhence the camera can be compact and low-priced. The smoothing circuiteliminates the signals at plus or minus side which are overlapped withAC components of the noise from the motor of the film feed means, andpicks out signals only at the other side which are not effected by thenoise, thereby correctly reading the voltage level. Moreover, bysmoothing the signals from the magnetic head, there is no necessity toraise the sampling frequency which specifies the timing for reading thevoltage level.

A low-pass filter is provided next to the smoothing circuit, andeliminates the noise caused by a change in a speed at which the filmfeed means feeds the film, thereby correctly reading the voltage level.

According to another embodiment of the present invention, the camera ofthe present invention further comprises a film position recognitionmeans for recognizing a position on the photographic film fed by thefilm feed means with respect to the magnetic head, and characterized inthat the film position recognition means recognizes an area in proximityof the center of each frame on the photographic film where there is ahigh possibility that some magnetic information is recorded if magneticinformation is recorded, and the magnetic information detecting meansperforms the detection only for the recognized area. Since there is somepossibilities that no magnetic information is recorded at front and backends of the magnetic record area for each frame, the regenerated signalsare read from the area in proximity of the center where there is a highpossibility that some magnetic information is recorded, so that whetherany magnetic information is recorded or not can be determined withoutfail.

According to yet another embodiment of the present invention, a magneticrecording and regenerating unit for photographic film, which has filmfeed means for feeding photographic film coated with a magneticrecording layer with a motor and has a magnetic recording function ofrecording magnetic information in the magnetic recording layer while thephotographic film is feeding and a magnetic regenerating function ofreading magnetic information recorded in the magnetic recording layer,the magnetic recording and regenerating unit comprises: a magnetic headfor accessing to the magnetic recording layer while the photographicfilm is feeding, the magnetic head including a coil wound around a core;a recording circuit for supplying recording current to the coil duringrecording, and an amplification circuit for amplifying signal voltagegenerated at ends of the coil during regenerating and thereby outputtingan regenerated signal, the recording circuit and the amplificationcircuit being connected to the ends of the coil in parallel; a referencevoltage apply means for applying reference voltage to the amplificationcircuit only during regenerating, the reference voltage apply meanscutting off the reference voltage from the amplification circuit duringa period except for regenerating; a driving power supply means forsupplying driving power to the amplification circuit during regeneratingand recording; and the magnetic recording and regenerating unit ischaracterized in that, during recording, the amplification circuitfunctions as a comparator to protect the amplification circuit frominput of signal voltage during recording.

According to the present invention, the single magnetic head in whichthe single coil is wound around the single core is used for bothrecording and regenerating, and the recording circuit and theamplification circuit for regeneration are directly connected inparallel to the ends of the coil. During regenerating, the drive powerand the reference voltage are supplied to an operational amplifier ofthe amplification circuit, and the amplification circuit functions asthe amplifier for regenerated signals. During recording, only the drivepower is supplied to the amplification circuit, and the referencevoltage is shut off. Thus, during recording, the amplification circuitfunctions as the comparator. If the signal voltage, which is applied tothe ends of the magnetic head during recording, is input to theamplification circuit, the amplification circuit is not broken. There isno necessity to provide the protection circuit, etc., which can be asource of noise, in the input stage of the amplification circuit. Thus,the noise and cost can be reduced.

According to another embodiment of the present invention, a magneticregenerating unit for a camera, which feeds photographic film coatedwith a magnetic recording layer and regenerates magnetic informationfrom the magnetic recording layer on the photographic film; the magneticregenerating unit for the camera comprises: a magnetic head foraccessing to the magnetic recording layer while the photographic film isfeeding, the magnetic head including a coil wound around a core, anumber of turns of the coil being determined so as to output aregenerated waveform which does not enable reading of the magneticinformation but permits determination of whether any magneticinformation is recorded or not; and a determination means fordetermining whether any magnetic information is recorded or not in amagnetic record area for each frame on the photographic film based onvoltage signals generated at ends of the coil.

According to another embodiment of the prevent invention, a camera whichloads therein a film cartridge containing photographic film coated witha magnetic recording layer, has film feed means for feeding thephotographic film from the loaded film cartridge with a motor,determines whether the loaded film cartridge is a partial cartridge,containing a photographic film having an exposed frame and an unexposedframe, or not, and feeds the photographic film from the loaded filmcartridge up to a first unexposed frame if determining that the loadedfilm cartridge is the partial cartridge; the camera comprises: amagnetic recording means for recording magnetic information in amagnetic record area on the magnetic recording layer corresponding to anexposed frame during one-frame feeding in every photographing; and anunexposed frame detecting means for detecting the first unexposed frameaccording to whether magnetic information is recorded in a magneticrecord area for each frame on the photographic film, the unexposed framedetecting means comprising a magnetic head for accessing to the magneticrecording layer while the photographic film is feeding, the magnetichead including a coil wound around a core, a number of turns of the coilbeing determined so as to output a regenerated waveform which does notenable reading of the magnetic information but permits determination ofwhether any magnetic information is recorded or not; and a determinationmeans for determining whether any magnetic information is recorded ornot in a magnetic record area for each frame on the photographic filmbased on voltage signals generated at ends of the coil.

That is, the magnetic recording and regenerating unit for thephotographic film is used when the partial cartridge is loaded again inthe camera. The magnetic recording and regenerating unit reads themagnetic information, which are recorded in the magnetic record area foreach frame on the photographic film, in order to detect the frame whichhas no magnetic information (unexposed frame). Thus, the regeneratedsignals are not needed for the purpose of perfectly reading the magneticinformation. Hence, the number of turns of the coil in the magnetic headcan be smaller so that the magnetic head can output the regeneratedwaveform to determine whether any magnetic information is recorded ornot, so in this case the magnetic head can be compact and low-priced.The number of turns of the coil is also determined so that the magnetichead can be used for recording the magnetic information.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature of this invention, as well as other objects and advantagesthereof, will be described in the following with reference to theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures and wherein:

FIG. 1 is a block diagram illustrating the construction of a cameraaccording to an embodiment of the present invention;

FIG. 2 is a schematic view of a magnetic head;

FIG. 3 is a view of assistance for explaining magnetic recordedpatterns;

FIG. 4 is a circuit diagram illustrating the first embodiment of arecording and regenerating circuit;

FIG. 5 is a timing chart of a process after the last magnetic data arerecorded;

FIG. 6 is a partially enlarged view of the timing chart in FIG. 5;

FIG. 7 is a view of assistance for explaining the direction in which thenoise of a motor is generated;

FIG. 8 is a waveform chart of signals which have passed through anamplification circuit (before smoothing);

FIG. 9 is a partially enlarged view of the waveform chart shown in FIG.8;

FIG. 10 is a waveform chart of the signals which have just passedthrough a smoothing circuit;

FIG. 11 is a waveform chart of the signals which have just passedthrough a low-pass filter;

FIG. 12 is a waveform chart of the signals which have just passed thelow-pass filter when resistances and condensers within the smoothingcircuit and the low-pass filter are changed;

FIG. 13 is a waveform chart of regenerated signals from a magnetic headwith a coil of 300 turns;

FIG. 14 is a waveform chart of regenerated signals from a magnetic headwith a coil of 1500 turns;

FIG. 15 is a flow chart of processes executed by the camera;

FIG. 16 is a flow chart showing battery checking of the camera;

FIG. 17 is a flow chart showing the sub-routine of a mid-roll change(MRC) control;

FIG. 18 is a circuit diagram illustrating an example of a temperaturemeasuring circuit;

FIG. 19 is a flow chart for determining whether the temperature issuitable or not for the MRC control;

FIG. 20 is a flow chart for determining whether the film is suitable ornot for the MRC control;

FIG. 21 is a flow chart for determining whether the film feed speed issuitable or not for the MRC control;

FIG. 22 is a flow chart for determining whether the motor current issuitable or not for the MRC control;

FIG. 23 is an enlarged view illustrating the construction of thephotographic film;

FIG. 24 is a flow chart showing another embodiment of the sub-routine ofthe mid-roll change (MRC) control;

FIG. 25 is a block diagram illustrating another embodiment of a circuitwhich determines whether there is any magnetic information recorded ornot;

FIG. 26 is a circuit diagram illustrating an example of a VR valueswitching circuit in FIG. 25;

FIG. 27 is a circuit diagram illustrating the second embodiment of therecording and regenerating circuit;

FIGS. 28(a), 28(b) and 28(c) are waveform charts for explaining theoperation of the recording and regenerating circuit in FIG. 27;

FIG. 29 is a flow chart showing the sub-routine of regenerated data(MRCAD) calculating process;

FIG. 30 is a circuit diagram showing the third embodiment of therecording and regenerating circuit;

FIGS. 31(a), 31(b), 31(c), 31(d) and 31(e) are waveform charts forexplaining the operation of the recording and regenerating circuit inFIG. 30;

FIGS. 32(a) and 32(b) are views of assistance for explaining thestructure of an advanced film cartridge; and

FIG. 33 is a circuit diagram illustrating the construction of aconventional magnetic head driver.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention will be described in further detail by way of examplewith reference to the accompanying drawings.

FIG. 1 shows the construction of a camera according to an embodiment ofthe present invention. This camera uses advanced cartridge roll filmshown in FIG. 32. After every photographing, a microcomputer 2 instructsa motor driver 3 to wind the film, and drives a motor 5 built in a spool4. When the motor 5 rotates, a drive transmission mechanism 6 rotatesthe spool 4 in a direction to wind the film, and photographic film 7starts feeding. Thereafter, the photographic film 7 is drawn out of thecartridge 8 to be taken up by the spool 4.

The drive transmission mechanism 6 also rotates a spool 8a of thecartridge 8. Just after the cartridge 8 is loaded in the camera, thedrive transmission mechanism 6 drives the spool 8a in a direction tofeed the film 7 and sends forth the photographic film from its end.Then, the end of the photographic film 7 is wound on the spool 4. Whenthe photographic film 7 feeds by the rotation of the spool 4 at higherspeed than speed at which the film is supplied by the rotation of thespool 8a of the cartridge 8, the spool 8a of the cartridge 8 rotates inassociation with the feeding of the film.

After the spool 4 has taken up a leader of the film, and the first framehas reached a photographing position, the motor 5 stops its movement.During rewinding, the motor 5 inverts to drive the spool 8a of thecartridge 8 in a direction to rewind the film, and the spool 4 rotatesin association with the spool 8a. Then, the photographic film 7 iscompletely rewound up into the cartridge.

Two perforations 7a, 7b are formed at each frame on the photographicfilm 7. For the first frame in particular, one more perforation isformed closer to the film leader from the perforation 7a. A reflexphotosensor 9 is provided above the film in the edge thereof where theperforations are formed, and a photoelectric signal from the photosensor9 is input to a PF (perforation) pulse generator 10. The PF pulsegenerator outputs a pulse signal every time the perforations 7a, 7b passthe front face of the photosensor 9, and the output pulse signal isinput to the microcomputer 2.

After receiving a photographing complete signal, the microcomputer 2drives the motor 5 via the motor driver 3 so as to start feeding thefilm. When the photosensor 9 detects the perforation 7a at the filmleader side, the film stops feeding to complete the feeding of the filmby one frame.

A transparent magnetic recording layer is formed on the whole surface atthe back of the photographic film 7, and a magnetic head 12 is drivenduring one-frame feeding of the film. A variety of information relatingto the date of photographing and the exposure, for example, aremagnetically recorded in a predetermined magnetic record area 11 foreach frame. When the information is recorded, characters and numberswhich compose the information are converted into binary codes, which aredigitally recorded.

A record regeneration circuit 15 generates data pulses of different dutyratios according to record signals supplied by the microcomputer 2during the recording. A magnetic head 12 magnetically records the datain the form of the binary code "1", "0" based on the data pulses.

During the magnetic recording, an encoder 16 and an ENC (encodement)pulse generator 17 are used so as to prevent a unit bit length fromchanging due to the film feed speed. The encoder 16 is composed of anencoder plate 16a and a photo-interrupter 16b. The encoder plate 16a isa disc which rotates in association with the feeding of the photographicfilm 7, and slits are radially formed on the disc at regular intervals.The photo-interrupter 16b photoelectrically detects the passage of theslit. The photo-interrupter 16b outputs a photoelectric signal whichfluctuates in synchronism with the feed speed of the photographic film7. The photoelectric signal is shaped by the ENC pulse generator 17, andthe shaped photoelectric-signal is input to the microcomputer 2 as anencodement pulse which is synchronous with the film feed speed. Forexample, the encoder plate 16a is 8 mm in circumference, and when theencoder plate 16a rotates once, 256 encodement pulses are generated. Theencoder plate 16a rotates three times during the one-frame feeding ofthe film.

During the magnetic recording, the microcomputer 2 transmits the recordsignals to the record, regeneration circuit 15 while clocking theintervals between the encodement pulses. Based on the transmittedrecord-signals, the record regeneration circuit 15 inverts a magneticfield which is generated by the magnetic head 12 in a timingcorresponding to "1", "0" of the binary code in the unit bit length ofthe magnetic recording.

During the magnetic regeneration, the microcomputer 2 reads the data ofthe regeneration signals from an A/D port in synchronism with the encodepulses.

The construction of the encoder is not restricted to the above, and theencoder plate may be attached to the spindle of the feed motor 5, andthe photo-interrupter may detect the passage of the radially-formedmultiple slits on the encoder plate.

A memory 18 in FIG. 1 has a ROM area and a RAM area. The ROM areacontains sequence programs for executing the above-stated magneticrecording and for reading the magnetic information on the magneticrecord area 11, and data for converting the information to bemagnetically recorded into the binary codes.

The RAM area temporarily contains data and flags for recording andregenerating the magnetic data. The magnetic recording method and theregeneration process will later be described in further detail (FIGS. 3and 17).

FIG. 2 shows an example of the construction of the magnetic head 12. Themagnetic head 12 consists of a single coil 14 of 300 turns wound on asingle core 13, and terminals 14a, 14b of the coil 14 are used for bothrecording and regenerating. The construction of the magnetic head 12 isnot restricted to the above-mentioned one with two terminals in FIG. 2.Two coils for recording and regenerating, respectively, may be wound ona single core, or two heads may be provided for recording andregenerating.

The magnetic head 12 in FIG. 2 consists of the single coil 14 wound onthe single core 13, and it can be used both as a recording head and aregenerating head. Thus, the magnetic head 12 has such an advantage thatno inductive current is generated on the regeneration side due to thecurrent flowing through the coil during recording. Moreover, since thecoil 14 is of only 300 turns, the magnetic head 12 can be compact (thin)and low-priced.

FIG. 3 shows an example of magnetic recorded patterns. 1 and 2 in FIG. 3show the timing for switching of potential of the terminals 14a, 14b ofthe coil 14 in FIG. 2, and I_(H) shows directions of the recordingcurrent flowing through the coil 14.

When the terminal 14a of the coil 14 is on a high level and the terminal14b is on a low level, the recording current I_(H) flows in thedirection of an arrow in FIG. 2 (a plus direction), and "N magnetizedarea" (an area in which magnetic flux turns to the right in the recordedpatterns illustrated in FIG. 3) is recorded in the magnetic recordinglayer. When the terminal 14a is on the low level and the terminal 14b ison the high level, the recording current I_(H) flows in the oppositedirection to the arrow in FIG. 2 (a minus direction), and "S magnetizedarea" (an area in which magnetic flux turns to the left in the recordedpatterns illustrated in FIG. 3) is recorded in the magnetic recordinglayer.

One recording period T for determining the unit bit length of themagnetic recording depends on a period in which the terminal 14a becomesthe high level. Pulse duration T_(D), which determines "1" and "0" ofthe binary code, depends on whether a termination of the "N magnetizedarea" is positioned at the first half or the second half of one recordperiod T. The microcomputer 2 outputs the record signal to the recordregeneration circuit 15 so that the pulse duration T_(D) can be equal toor greater than T/2 when recording "1" of the binary code, and the pulseduration T_(D) can be less than T/2 when recording "0" of the binarycode.

FIG. 4 shows the first embodiment of the record regeneration circuit 15.

The record regeneration circuit 15 is composed mainly of a power sourcecircuit 15a, a regenerating circuit 15b and a recording circuit 15c. Thepower source circuit 15a includes a battery 20, which is also used as apower source for opening and closing shutter blades and feeding the filmduring photographing. For example, a lithium battery of 3 V is used asthe battery 20. A step-up circuit 21 is able to obtain a voltage of 5 V,a regulator 22 is able to obtain voltages of 5 V and 4.1 V, and aregulator 23 is able to obtain a voltage of 2.3 V.

An output port of the regulator 23 connects to a switching transistor24, and the base terminal of the transistor 24 connects to a MRCON portof a camera CPU, which is equivalent to the microcomputer 2 in FIG. 1.

When the unexposed frames remaining in the loaded film cartridge 8 areconfirmed, the MRCON port outputs a low level (L) signal. When the baseterminal of the transistor 24 is grounded, a reference voltage of 2.3 Vis applied to an amplification circuit 30 of the regenerating circuit15b. Two condensers 25, 26 within the power source circuit 15a preventhigh frequency noise from overlapping with the reference voltage 2.3 Vfrom the regulator 23.

The regenerating circuit 15b consists of the magnetic head 12, theamplification circuit 30, a smoothing circuit 32 and a low-pass filter33. The amplification circuit 30 has a resistance 35 for converting theregenerated current flowing through the coil 14 of the magnetic head 12into regenerated signals, and operational amplifiers 36, 37, 38 whichnon-inverting amplify the signal voltage obtained from the resistance35. The operational amplifiers 36, 37, 38 may be ones available on themarket, and a protective resistance is preferably incorporated into aninput stage of each operational amplifier in order to prevent anelectrostatic breakdown.

The operational amplifier 38 is provided with a condenser for cuttingthe high frequency noise In FIG. 4, the signal voltage is amplified inthree steps by means of three operational amplifiers, but theconstruction of the amplification circuit 30 is not restricted to this.The amplification circuit may be an integrated circuit.

The drive power of 5 V is supplied to the power supply lines of theoperational amplifiers 36, 37, 38 from the output port (V_(OF) port) ofthe regulator 22, and the reference voltage of 2.3 V is applied toinversion input terminals of the operational amplifiers 36, 37, 38 fromthe output port of the regulator 23. The amplification circuit 30 isdriven by three types of voltage: the drive power "+V_(CC) (5 V)" fromthe regulator 22, "-V_(CC) (GND)", and the reference voltage (2.3 V)from the regulator 23. As shown in FIG. 4, using two regulators resultsin stabilizing the ground of the operational amplifiers.

The regulator 22, which supplies the drive power to the amplificationcircuit 30, is controlled according to instruction signals from thecamera CPU. The drive power is supplied to or cut off from theoperational amplifiers 36, 37, 38 according to the instruction signals.Specifically, the drive power is supplied while the instruction is givento feed the film, and the drive power is cut off while the film stops.When the drive power is not supplied, the amplification circuit 30 isinactive. If the signal voltage in writing (recording) is input to theinactive operational amplifiers 36, 37, 38, there is a possibility thatthe operational amplifiers 36, 37, 38 can be broken. Thus, the drivepower is always supplied to the amplification circuit 30 duringrecording. Since the motor 5 is always driven during magnetic recording,the drive power is supplied to the amplification circuit 30 when themotor 5 is driven.

As stated above, the drive power of 5 V is supplied to the amplificationcircuit 30 not only when the magnetic information is regenerated (read)but when the magnetic information is recorded (written). Thereby, theoperational amplifiers 36, 37, 38 which are not provided with thereference voltage from the regulator 23 can be used as comparators, sothat the operational amplifiers 36, 37, 38 can be protected.

According to the above construction, the breakdown of the operationalamplifiers can be prevented, and there is no necessity to provide aprotective circuit in the input stage of the amplification circuit 30.Moreover, there is no necessity to provide a switch, etc. forelectrically cutting off the amplification circuit 30 from the magnetichead 12 during recording. Thus, the noise and cost can be reduced.

The smoothing circuit 32 comprises a diode 40, a condenser 41 and aresistance 42, and it smoothes an electric signal amplified by theamplification circuit 32. In order to recognize a position of anunexposed frame by means of the magnetic information recorded in themagnetic recording layer on the photographic film, it is simplydetermined whether the magnetic information is recorded or not. There isno need to correctly read the contents of the magnetic information, thatis, "1" and "0" of the binary code. For this reason, the signalamplified by the amplification circuit 30 is smoothed to obtain anenvelope waveform, and it is determined whether there is any magneticinformation recorded or not, according to the obtained envelopewaveform.

In this case, the signal obtained via the magnetic head 12 includesnoise components induced by the film feed motor 5. The noise generationof the motor 5 will later be described in detail (FIG. 7). An ACcomponent of the noise from the motor 5 appears at one of plus side andminus side of the signal according to a positional relationship betweenthe motor 5 and the magnetic head 12. In this embodiment, the motor 5 isarranged so that the AC component appears at the plus side of thesignal, and the diode 40 in the smoothing circuit 32 is arranged in amanner to eliminate the AC component from the noise of the motor 5 asshown in FIG. 4. Thereby, the negative side (one side) of the signal ispicked up.

The noise overlapping with the signal results from not only the noise ofthe motor 5 but the unevenness in the film feed speed. The faster thefeed speed of the photographic film 7 is, the higher the signal outputwill be. The slower the feed speed is, the lower the signal output willbe. Thus, if the feed load is increased because the film gets old orhard, the change in the feed speed results in the change in the signaloutput. In order to eliminate the noise resulting from the unevenness ofthe film feed speed, there is provided the low-pass filter 33 next tothe smoothing circuit 32.

The low-pass filter 33 is composed of a resistance 44 and a condenser45, and combination of the resistance 44 and the condenser 45 can set acutoff frequency. For example, if the low-pass filter 33 has a lowcutoff-frequency of approximately 16 Hz, the effects of the change inthe film feed speed can be eliminated.

The regenerated signal passing through the low-pass filter 33 is sent toan A/D port (MRCIN) of the microcomputer 2, which determines whetherthere is any magnetic data or not according to the sent regeneratedsignal. A method of determination will be described later.

The reading of the regenerated signal supplied to the A/D port (MRCIN)of the microcomputer 2 is synchronous with the encodement pulses fromthe encoder 16. In this case, after detecting the edge of theperforation 7a, the regenerated signals are disregarded during thenumber of the encodement pulses from the encoder 16 is counted for apredetermined number, for example 256 pulses. After disregarding thedata of 256 pulses, the magnetic information is read from the A/D port.

Because the magnetic information is very likely to be recorded in anarea close to the center between the perforations 7a, 7b in the magneticrecord area 11 of each photo frame, the magnetic information is read(measured) 256 times after a predetermined amount (256) of pulses areread from the end of the magnetic record area 11. Then, the signal levelis determined based on an average or integration of the data which areread 256 times. Thus, by limiting area for reading of the magneticinformation for detecting whether there is any magnetic information tothe center area, the existence of any magnetic information can bedetected without fail.

Before reading the magnetic information of photo frames, the referencedata are obtained based on an average or integration of data which areread 256 times. If the encoder 16 is attached to the spindle of the feedmotor 5, the reference data can be obtained just after the motor 5 isdriven, before the photographic film 7 contacts the magnetic head 12.

Description will hereunder be given of the recording circuit 15c of therecord regeneration circuit 15.

The magnetic head 12 connects to the recording circuit 15c in parallelwith the amplification circuit 15b. While the photographic film 7 isfeeding, the recording circuit 15c is able to write the magneticinformation in the magnetic recording layer on the photographic film 7.

The recording circuit 15c magnetically records the information bycontrolling the direction of the recording current flowing through thecoil 14 of the magnetic head 12. The magnetic head 12 is driven bybridge-connected switching transistors 50 (the first switchingtransistor), 51 (the second switching transistor), 52 (the thirdswitching transistor), and 53 (the fourth switching transistor). Controltransistors 54, 55 control ON/OFF of these switching transistors 50, 51,52, 53.

The base terminals of the control transistors 54, 55 connect to a MHCport and a MHD port, respectively, of the microcomputer 2. Duringmagnetic recording, the high and low signals are supplied to the MHCport and the MHD port oppositely, so that the control transistors 54, 55are turned on and off.

The base terminal of the switching transistor 50 of the recordingcircuit 15c connects to the output port (V_(AF) port) of the regulator22 via a resistance 58. Thereby, the action of the switching transistor50 can be stabilized by providing a pull-up circuit.

If there is no pull-up circuit, the base and the collector of theswitching transistor 50 are free, and the action of the switchingtransistor 50 is unstable. The MHC port and the MHD port are low levelduring regeneration. The battery 20 applies the power of 3 V to theemitter of the switching transistor 50. When the slight current flowsbetween the emitter and the collector of the switching transistor 50 dueto the noise, etc., a current flows from the battery 20. The current isamplified by the amplification circuit 30, and it overlaps with theregenerated signals of the current generated by the magnetic head 12.For example, during regeneration, if the current generated at therecording circuit 15c is so small as of few nA, the current is amplifiedto the signal level by the operation of the amplification circuit 30.

Thus, the current from the recording circuit 15c must be completely cutoff during regeneration. For this reason, the base terminal of theswitching transistor 50 is provided with the above-mentioned pull-upcircuit, and the potential is applied to the base of the switchingtransistor 50 from the regulator 23 while the film is feeding.

Since the reference voltage of 2.3 V is applied to the collectorterminal of the switching transistor 51 at the right in the drawingduring regeneration, the action of the switching transistor 51 canalways be stable, and thus there is no need to provide the pull-upcircuit.

Description will hereunder be given of the operation of the recordingcircuit 15c during recording. The clock pulses and the data pulses fromthe microcomputer 2 switch the MHC port and the MHD port to high leveland low level oppositely, and the switching transistors 54, 55 areselectively turned on and off. When, for example, the switchingtransistor 54 is tuned on and the switching transistor 55 is turned off,the control transistors 50, 53 are turned on, and the recording currentI_(H) flows through the coil 14 of the magnetic head 12 in the directionof the arrow in FIG. 2. Then, "N magnetized area" is recorded in themagnetic record area 11 on the photographic film 7. To the contrary,when the switching transistor 54 is turned off and the switchingtransistor 55 is turned on, the control transistors 51, 52 are turnedon, and the recording current I_(H) flows through the coil 14 in thedirection opposite to the direction of the arrow in FIG. 2. Then, "Smagnetized area" is recorded in the magnetic record area 11.

The amount of the recording current I_(H) flowing through the coil 14depends on the voltage of the battery 20, which is the power source, aresistance 60 (or a resistance 61), and a resistance of the coil 14. Theresistance of the coil 14 of the magnetic head 12 in FIG. 4 is aboutseveral dozens Ω, which is very small compared to a resistance ofseveral hundreds Ω of a coil of a magnetic head in the conventionalaudio equipment.

One of the protective resistances 60, 61 connects to the coil 14 inseries according to the direction of the current, thereby preventing theexcessive current from flowing through the coil 14 during recording andregenerating. The diameter of wire composing the coil 14 and the numberof turns of the coil 14 are determined so that the resistance of thecoil 14 can be several dozens Ω, and the number of ampere-turns (AT) canbe more than 3, more preferably more than 5 for proper magneticrecording and regenerating.

The recording circuit 15c is provided with a brake circuit, whichincludes transistors 72 (the fifth switching transistor) and 73 (thesixth switching transistor). The base terminals of the transistors 72,73 connect to a MHB port of the microcomputer 2. A high level signal ofone pulse is supplied to the MHB port after magnetic recording, so thatthe transistors 72, 73 can be turned on. Thereby, both ends of the coil14 are short-circuited, and the bridge circuit composed of thetransistors 50, 51, 52, 53 simultaneously discharges the electric chargewhich is accumulated in proximity of the magnetic head 12, therebypreventing the unstable recording current from flowing through the coil14. In this case, the resistance 60, 61 in the bridge circuit act as theprotective resistances, thereby preventing the excessive current fromflowing through the bridge circuit.

According to the above-described construction, the stray electric chargearound the magnetic head 12 is cleared on completion of magneticrecording, so that the non-magnetized area can be formed without failafter the end recording, and the recording errors resulting from thenoise can be eliminated.

FIG. 5 is a timing chart showing a process after recording the lastmagnetic data, and FIG. 6 is an enlarged view of the essential parts ofFIG. 5.

After recording the data of the last bit, an end recording process isexecuted. In the end recording process, the MHC port becomes the H leveland the MHD port becomes the L level for a period of the pulse durationT_(D) of the data pulse which is input to the MHD port when the data ofthe last bit are recorded, and thereby "N magnetized area" is recorded.Then, "S magnetized area" is recorded at the rear end of the binary dataof the last bit. Thereafter, the MHC port becomes the H level and theMHD port becomes the L level in order to record "N magnetized area" (endrecording).

As shown in FIG. 6, the MHB port is turned on (high output) just before(several μs) the clock pulse of the MHC port switches to low level afterthe clock pulse of the MHC port becomes high level and a predeterminedperiod of time (more than 80 μs) has passed. Thereby, the transistors72, 73 are turned on, and the unnecessary electric charge is dischargedfrom the area in proximity of the magnetic head 12, so that therecording errors resulting from the oscillating current can beprevented.

Thereafter, the output of the MHB port is turned off after apredetermined period of time (more than 80 μs).

Next, an explanation will be given of the noise generating power of themotor 5.

FIG. 7 shows a relation between the arrangement of magnets in the motor5 and leakage magnetic flux. The leakage magnetic flux includes ACcomponents and DC components, and the magnetic head 12 is affectedmainly by the AC components. As shown in FIG. 7, the AC components aregenerated by switching NS of a rotor, the direction in which the ACcomponents are increased is shifted by 90 ° from the direction in whichthe DC components are increased. In substantially the same direction asthe direction in which the AC components are increased, brush noise isgenerated due to the rapid change of a contact between brushes and acommutator.

If the angle (direction) of the motor 5 in the spool 4 of FIG. 1 ischanged around the axis, the noise rapidly changes around an angle wherethe noise is decreased, and thus the noise is difficult to estimate. Onthe other hand, the change in the noise is stable around an angle wherethe AC components including the brush noise are increased. Moreover, theAC components are restricted to the noise at one side of the plus sideand the minus side.

For the reasons stated above, the positional relationship between themotor 5 and the magnetic head is determined in a manner to generate thenoise at one side (the plus side), and the diode 40 in the smoothingcircuit 32 eliminates the noise (AC components) generated at the plusside.

If the positional relationship is determined so that the noise isgenerated at the minus side, the diode in the smoothing circuit 32 turnsto the forward direction, and thereby the signal at the upper side (theplus side) is picked up.

An explanation will hereunder be given of the operation of the recordregeneration circuit 15 in FIG. 4 during regeneration with reference towaveform charts.

FIG. 8 shows an example of signals just after passing through theamplification circuit (before smoothing). The horizontal axis isgraduated in approximately 50 ms. The area in which the amplitude islarge represents the magnetic data recorded in the magnetic recordinglayer, and the area in which the amplitude is relatively smallrepresents an area where there is no magnetic information (for example,an area between two frames). The noise of the motor 5, etc. effects thearea where there is no magnetic data.

FIG. 9 is an enlarged view of the area with magnetic data. Thehorizontal axis is graduated in approximately 1 ms. As shown in FIG. 9,the magnetic data are composed of the clock pulse whose polarity hasbeen inverted and the data pulse which has a different duty ratio fromthe clock pulse.

FIG. 10 is a waveform chart describing the case when the smoothingcircuit 32 smoothes the signals in FIGS. 8 and 9, which have passedthrough the amplification circuit 30, and only one side (the negativeside) is picked up. FIG. 11 shows the signals of which noise componentsare eliminated by the low-pass filter 33. In FIGS. 10 and 11, thehorizontal axis is graduated in approximately 0.2 ms.

FIG. 12 illustrates another example of the regenerated signals in thecase of changing the combination of the resistances 42, 44 and thecondensers 41, 45 of the smoothing circuit 32 and the low-pass filter33. As understood by comparing to FIG. 11, the performance of thesmoothing circuit 32 and the low-pass filter 33 depends on thecombination of the resistance 42, 44 and the condensers 41, 45. A propercombination is selected to form proper signals to be input to the A/Dport in FIG. 4.

This embodiment employs the magnetic head 12 with the coil of 300 turnsso that camera can be compact (thin) and low-priced. For example, aconventional regeneration head with a coil of 1500 turns is about 6.5 mmhigh. The magnetic head with a coil of 300-600 turns is about 2 mm high(H), which is advantageous to make the camera compact. The more thenumber of turns of the coil is, the larger and more expensive themagnetic head is.

FIG. 13 is a waveform chart of the regenerated signals from the magnetichead 12 with the coil of 300 turns, and FIG. 14 is a waveform chart ofthe regenerated signal from the magnetic head with the coil of 1500turns. If the data pulse of "0" or "1" is represented by the pulse whichis opposite to the clock pulse recorded at the first half or the secondhalf of one period of the clock pulse, the phase of the data pulse mustbe correctly read. If the magnetic head with the coil of 300 turns isused as the regenerating head, it is difficult to read the phase becausethe obtained regenerated waveform loses its shape. If, however, themagnetic information is regenerated in order to detect the firstunexposed frame on the partially exposed film contained in the partialcartridge, whether any magnetic information is recorded or not in themagnetic recording layer is determined. There is no necessity tocorrectly read the contents of the magnetic information, that is, "1"and "0" of the binary code. Hence, the magnetic head with the coil of300 turns can be used as the regenerating head.

If the number of turns of the coil is further decreased, the level ofthe regenerated signal is lowered, and the noise is equal to the signallevel or more than the signal level, and the existence of theregenerated signal cannot be confirmed. TABLE 1 shows an example of arelation between the number of turns and signal recognition.

                  TABLE 1                                                         ______________________________________                                        Number of turns                                                                          Signal recognition (present conditions)                            ______________________________________                                        more than 1000                                                                           "0" and "1" can be recognized.                                     300-1000   "0" and "1" cannot be recognized, but the                                     existence of the signal can be recognized.                         less than 300                                                                            The signal may be hard to detect in the noise. If,                            however, the regeneration is prohibited when the                              signal is difficult to regenerate, the coil of up to                          100 turns can be used.                                             ______________________________________                                    

Accordingly, this embodiment employs the magnetic head with the coil of300 turns. If it is impossible to read "0" and "1" but possible tooutput the regenerated waveform for determining the existence of themagnetic data, the magnetic head is not restricted to 300 turns. Sincethe magnetic head having the coil of large number of turns is hardlydriven when used as the recording head, the number of turns ispreferably small. The number of turns is preferably between 100 and 600in order to use the magnetic head as the recording head by decreasingthe number of turns and make the camera compact and low-priced and tooutput the regenerated waveform for determining the existence of themagnetic signals recorded.

Description will hereunder be given of the operation of the camera whichis constructed in the above-mentioned manner with reference to the flowchart of FIG. 15.

When the film cartridge 8 is loaded in the camera, DEP/DD process isexecuted first (Step S11 hereinafter only numerals will be denoted). Inthis process, an optical reader reads a bar code on a data disk providedin the loaded cartridge, thereby obtaining the information such as thefilm sensitivity, the film type and the number of prints available (DDcontrol). Then, the position of the white plate which is exposed inwhite for the VEI is detected, and thereby the status of the loadedcartridge 8 is detected (DEP reading). The above-mentioned informationis stored in a predetermined area of the memory 18.

In S11, the battery is checked as shown in the flow chart of FIG. 16. Asshown in FIG. 16, the load current flows for battery checking (BC)(S111). After a waiting time for stabilizing the battery voltage haspassed (S112), the voltage level of the battery is read from the A/Dport (S113). Then, an A/D value to which the battery voltage is A/Dconverted is compared to the first and second threshold levels (S114).The first threshold level is for prohibiting the photographing, and thesecond threshold level is higher than the first threshold level. At thesecond threshold level, the photographing is possible but the exhaustionof the battery is warned. At a proper voltage level of the battery forexecuting the photographing, the film can be smoothly fed at least oneframe so that the magnetic recording can be performed during one-framefeeding after photographing.

If the A/D value of the battery is higher than the second thresholdlevel, the battery check is approved (BC OK) (S115). After the loadcurrent is canceled (S119) to complete the BC control. On the otherhand, if the A/D value of the battery is lower then the second thresholdlevel but higher than the first threshold level, a BC warning is displayand a BC warning flag is set (S116, S117). If the A/D value of thebattery is lower than the first threshold value, a BC NG is display anda BCNG flag is set to prohibit the photographing (S116, S118). When theBCNG flag is set, the camera is prohibited from taking any actionsthereafter. The above-mentioned battery checking is performed in eachprocess described later, and it is also performed when the shutterrelease button is operated and just before the film is rewound.

As shown in FIG. 15, at S12, it is determined whether the loaded filmcartridge is the partial cartridge or not, according to the used statusdetected at S11. In the case of the film cartridge is the partialcartridge, a process called a mid-roll change (MRC) control is executed(S13). A sub-routine of the MRC control will be described later (FIG.17).

If it is determined that a cartridge other than the partial cartridge isloaded at S12, the process goes on to S14, and it is determined whetherthe film cartridge has already been used or not. If the film cartridgehas already been used, it is determined as being incapable ofphotographing. Without executing such process as film feeding, etc. theprocess goes on to (A) in the drawing. That is, in the VEI control, thespool 4 and the sectorial white plate move to a predetermined positionto set the exposure of the cross in white so as to indicate that thefilm has already been exposed, and the loading operation of thecartridge is completed.

On the other hand, if the loaded cartridge has not been used yet, aframe set flag is stored in a predetermined area of the memory 18 toindicate the number of all photo frames N_(max) in accordance with theinformation obtained during the DD control. The film is fed according tothe value N_(max) of the frame set flag. That is, first frame setting(FFS) is executed such that the film feeds to the first photo frame(S15).

After the first frame setting control (S15) or the MRC control (S13),the strobe charging is controlled (S16), and the initial value of thecamera is set (S17).

Thus, preparations for photographing are completed. Thereafter, thestate of a manual rewind (MR) switch is confirmed (S18). The MR switchrewinds the film into the cartridge in such a state that there are someunexposed frames. Unless the user turns on the MR switch, the MR switchis off.

If the MR switch is off, the state of the release switch is determined.That is, whether the shutter release switch is pressed or not isdetermined. If the release switch has not been pressed, the processreturns to S18. If the release switch has been pressed, the shuttercontrol (S21) is executed after the automatic exposure/automaticfocusing (AE/AF) control (S20). The magnetic data such as photographingconditions with respect to the photographed frame are set in the RAM(S22), and then the writing of the magnetic information is controlledduring the automatic winding of one frame (S23).

Specifically, the MHC port and the MHD port are H/L controlled and L/Hcontrolled, respectively. "N magnetized area" and "S magnetized area"are formed in the magnetic record area 11 of each frame. In this case,the MRCON port is turned off (H output), and the reference voltage isnot supplied to the amplification circuit 30. The VOF port of theregulator 22 is on (5 V output). For this reason, the amplificationcircuit 30 functions as a comparator, thereby protecting the operationalamplifiers 36, 37, 38.

After the last binary data are recorded, the high-level signal issupplied to the MHB port, and both ends of the coil 14a of the magnetichead 12 are short-circuited. Thus, just after the last binary data arerecorded, the non-magnetized area can be formed without fail, therebypreventing the recording errors resulting from the noise.

Then, whether all the frames have been exposed or not is confirmed(S24). If not, that is, if there are some frames unexposed, the processreturns to S18 as shown in (B) in the drawing. On the other hand, if thephotographing (exposing) of all frames is complete, the film isautomatically rewound in the rewind control (S25). In this case, thespool 4 and the white plate are moved to a predetermined position in theVEI control, thereby setting the exposure of the cross indicating thatthe all frames have already been exposed.

When the MR switch is turned on at S18, the rewind process (rewindcontrol) is executed (S28). That is, the motor 5 is inverting driven,and the drawn-out film is rewound into the cartridge, and thelight-shielding lid is closed. In this case, whether the film hasalready been used or not is confirmed (S29). In the case of the unusedfilm, the process is completed after setting the exposure of the circlein white in the VEI control so as to indicate that the film has not beenused yet (S30). In the case of the film which has already been used, theprocess is completed after setting the display of the semi-circle in theVEI control so as to indicate that there are some unexposed framesremaining (S31). Thus, when the film cartridge is taken out of thecamera, the status of the film can be easily confirmed.

Description will hereunder be given of the MRC control.

If detecting the loading of the partial cartridge, the process goes onto a sub-routine of the mid roll change (MRC) control shown in FIG. 17.

After the start of the MRC control, it is determined whether the MRCcontrol may be executed or not in an optional determination A (S40A). Inthis optional determination A, the temperature within the camera isdetected first.

FIG. 18 is a circuit diagram illustrating an example of a temperaturemeasuring circuit. As shown in FIG. 18, the temperature measuringcircuit consists of a transistor Tr, which is turned on when thetemperature is measured, and a temperature dependent diode D, etc. Whena TEMPON signal (a L level signal) is supplied to control ON/OFF of thetransistor Tr, the temperature measuring circuit outputs a signal TEMPADaccording to the temperature within the camera. Then, an A/D value(TEMPAD value) of the signal TEMPAD is supplied to the camera CPU (notshown). The camera CPU determines whether the temperature is proper forthe MRC control in accordance with the flow chart in FIG. 19.

When the temperature is measured, the camera CPU supplies the signalTEMPON of the L level to the transistor Tr, thereby turning on thetransistor Tr (S201). After a waiting period (10 ms) has passed tostabilize the measurement of the temperature (S202), the TEMPAD value isread from the A/D port (S203). Then, the TEMPAD value is compared to aconstant C which is a TEMPAD value at a predetermined referencetemperature (for example, approximately 1.4 V obtained in an experimentat temperature of -10 ° C.). If the TEMPAD value is more than C, thetemperature is determined as NG, and if the TEMPAD value is equal to orless than C, the temperature is determined as OK (S204).

If the temperature is determined as NG, the process is completed aftersetting the display of the semicircle in white in the VEI control ofFIG. 17 (S43) via a flow line (C). If the temperature of thephotographic film is lowered, the flexibility of the photographic filmis decreased, which results in the irregular feeding. Thus, there is apossibility that the magnetic regeneration cannot be satisfactorilyperformed during the MRC control.

In the optional determination A, the type of the film cartridge is alsodetermined. As shown in FIG. 20, it is determined whether the filmcartridge loaded in the camera contains color negative film (CN) orcolor reversal film (CR) (S210) according to the information obtainedduring the DD control. If the film cartridge contains the CR film, thecartridge is determined as NG and the process returns to the flow line Cof FIG. 17. Since the magnetic layer of the CR film is thinner than thatof the CN film, it is not proper for the MRC control.

When the optional determination A is approved as stated above, a batterychecking (BC) control is executed (S41). In the battery checking, theoutput voltage of the battery 20 is measured while the load currentflows, and the measured voltage is compared to a predetermined thresholdlevel. If the output voltage of the battery 20 is less than thethreshold level, the state is determined as BCNG. Then, BCNG isdisplayed, and the BCNG flag is set.

In this embodiment, the threshold level for determining BCNG in the MRCcontrol is the second threshold level (e.g. the threshold level set towarn the exhaustion of the battery) which is higher than the firstthreshold level for determining BCNG described with reference to FIG.16. When the partial cartridge is loaded in the camera, the exposedframes and unexposed frames must be distinguished, and the photographicfilm must be fed to the first unexposed frame, thus requiring muchelectricity to prepare for photographing. In particular, since theexposed frames and unexposed frames are distinguished according to themagnetic information recorded in the magnetic recording layer on thephotographic film, the photographic film needs to be smoothly fed at apredetermined speed.

If the state of the BCNG flag is determined at S42 in FIG. 17 and theBCNG flag is set, the electricity required for processing such as filmfeeding cannot be obtained. The process is completed after setting thedisplay of the semicircle in white indicating that there are some framesunexposed in the VEI control (S43).

In this embodiment, the threshold level for determining BCNG in the MRCcontrol is different from the threshold level for determining BCNGdescribed with reference to FIG. 16. The present invention, however,should not restricted to this. Whether the BC warning flag is set or notmay be determined at S42 with the threshold level in the batterychecking unchanged. That is, if the BC warning flag is set in the MRCcontrol, the camera may be prohibited from taking any actions.

If the BCNG flag is not set at S42, that is, if the residual amount ofthe battery is more than a predetermined amount, the motor 5 is drivenforward to feed the film forward (FWD) (S44). In this case, the V_(OF)terminal of the regulator 22 in FIG. 4 outputs the voltage of 5 V, andthe drive power of 5 V is supplied to the amplification circuit 30.

After confirming the MHC port and the MHD port of the microcomputer 2 asbeing low (L) output (S45), MRCON port is turned into L output (S46). Byturning on MRCON, the reference voltage is supplied to the operationalamplifiers 36, 37, 38 of the amplification circuit 30, which amplifiesthe signal generated by the magnetic head 12.

The A/D value which is supplied to the MRCIN port before thephotographic film 7 contacts the magnetic head 12 or while the filmleader with no magnetic information is feeding, is read as referencedata (S47). The reference data are read 256 times in synchronism withthe encodement pulses, and a reference value (MRCREF) is obtainedaccording to the average or integration of the data.

As shown in FIG. 1, the perforations 7a, 7b are formed at the front andthe rear of each frame on the photographic film 7, and one moreperforation is formed closer to the front edge of the film from theperforation 7a. Thus, two perforations are formed at the head of eachframe. The perforation of the two perforation which is closer to thefront edge of the film is referred to as the first perforation, and thefollowing perforation is referred to as the second perforation. Whetherthe edge of the second perforation has passed or not is confirmed basedon an output of the photosensor 9 (S48). Just after confirming thepassage of the second perforation, the counting of the encoder pulsesfrom the encoder 16 is started.

At that time, whether the MRC control may be executed or not isdetermined in an optional determination B (S40B). As shown in FIG. 21,the period of the encoder pulse during the feeding is measured in theoptional determination B. If the period T is larger than a referenceperiod D (constant) (i.e. T>D), the film feed speed is determined asbeing lowered, that is, NG (S220), and the process returns to the flowline C of FIG. 17. If the feed speed of the photographic film is lowerthan a predetermined reference speed, S/N deteriorates.

Likewise, in the optional determination B, the A/D value (MDCAD) is readfrom the A/D port for battery checking (BC) as shown in FIG. 22 (S230).Then, it is determined whether MDCAD is smaller than a predeterminedreference value (the A/D value on BC) or not (S231). When MDCAD issmaller than the reference value, the film feed load is larger than theload in BC (battery checking is usually performed with the maximum loadapplied). In this case, the film feeding is determined as NG, and theprocess returns to the flow line C of FIG. 17.

In an embodiment described with reference to FIG. 22, the amount of thefilm feed load is determined based on the voltage of the battery;however, the present invention should not be restricted to this. If themeasured current of the motor is larger than a predetermined referencevalue (e.g. the motor current value which is measured during normalfeeding), the film feed load may be determined as being large. The motorcurrent can be found by measuring a voltage drop with a potentialdifference meter when the measured current flows to a resistor.

If the optional determination B (S40B) is approved, the counted value(ENCOUNT) which is counted at S49 is compared to a predeterminedconstant A (e.g. 256) (S50). If the counted value (ENCOUNT) is smallerthan the constant A (e.g. 256), the process returns to S49. When thecounted value reaches 256, the A/D value of the MRCIN port is read(S51). In this embodiment, the data of 256 pulses are disregarded toobtain the data in proximity of the center of the magnetic record area;however, another constant A may be set if the data in proximity of thecenter of the magnetic record area can be obtained.

The A/C value is read 256 times in synchronism with the encoder pulsesat step S51, and regenerated data (MRCAD) are obtained based on theaverage or integration of the data.

Thereafter, MRCADC is found by adding a predetermined constant B to theregenerated data (MRCAD) (S52), and the difference or ratio between theregenerated data MRCADC including the margin (the constant B) and thereference MRCREF is found (S53). If the regenerated data are smallerthan the reference, it indicates that the magnetic information isrecorded in the frame, that is, the frame has already been exposed. Thefilm count number is incremented by one frame (S54), and the processreturns to S48.

On the other hand, at S53, if the regenerated data are larger than thereference, it indicates that the magnetic information is not recorded inthe frame, that is, the frame has not been exposed yet. The film stopsfeeding (S55). Then, the rewinding is controlled (S56), and the film isrewound until the first perforation of the frame count number passes(S57).

When the first perforation of the frame count number is detected at S57,the motor 5 rotates forward again, and the film feeds forward (S58).When the second perforation of the frame count number is detected, thedriving of the motor 5 is stopped (S59). Then, the process returns tothe main routine shown in FIG. 15, and the process following the strobecharging (S16) is executed.

As stated above, after exposing the frames to half of the roll ofphotographic film 7, the camera is able to rewind the exposedphotographic film 7 into the cartridge 8 and then take out thephotographic film from the cartridge 8. When the partial cartridge isloaded in the camera, the position of the unexposed frame on the film isfound by detecting whether there is any magnetic information recorded inthe magnetic recording layer of each frame, so that the photographingcan be performed again from the unexposed frame.

In this embodiment, if one of four results of the optional determinationA or B (shown in FIGS. 19-22) is NG, the MRC control is not performed.The present invention, however, is not restricted to this. Anothercondition may be set that, for example, the MRC control is performedeven if one of the determination results is NG, and the MRC control isnot performed if two or more of the determination results are NG. Thereset timing, the number of measuring MRCNAD, etc. are not restricted tothe above-described embodiment. Instead of using the average value, theintegrated value may be compared to a reference value.

In this embodiment, the A/D value which is supplied to the MRCIN portwhile the film leader is feeding, is read as the reference data (S47).The present invention, however, is not restricted to this. The referencedata may be read from another part where there is no magneticinformation recorded.

That is, as shown in FIG. 23, the magnetic record area 11 for each frameis positioned inward by a predetermined amount .increment.d from theedge at the inside of each of the perforations 7a, 7b which specifieseach end of a frame. The information relating each frame is magneticallyrecorded only in the corresponding magnetic record area 11. Thus, themagnetic information is not recorded in areas 19, which are indicated byalternate long and short dash lines, in front of the magnetic recordarea 11 of the first frame and between the magnetic record areas 11.

Accordingly, a signal which is obtained while the magnetic head 12contacts the area 19 with no magnetic information recorded may be usedas reference data.

The reference data can be obtained at any position in the area 19 withno magnetic information recorded. The reference data are preferablyobtained when the reading part of the magnetic head 12 is positioned atthe first or second perforation, that is, within the width of the firstor second perforation.

The perforations 7a, 7b are about 2 mm wide in the direction to feed thefilm. After the photosensor 9 detects the edge of the perforation 7a or7b, the reference data are obtained within next 2 mm (e.g. 1 mm).

Description will hereunder be given of a procedure for obtaining thereference data in the above-mentioned area in MRC control with referenceto a flow chart of FIG. 24. The steps similar to those in the MRCcontrol in FIG. 17 are denoted by the same reference numerals, and theywill not be described in detail.

The MRC control shown in FIG. 24 has additional steps of obtaining thereference data (instead of S47, the steps from S60 to S64 areperformed).

That is, in order to obtain the reference data, a counter value(ENCOUNT) of the counter, which counts the encodement pulses of theencoder 16, is initialized at "0" (S60). At S61, whether the front edgeof the second perforation has passed or not is confirmed according tothe output of the photosensor 9. On confirmation of the arrival of thesecond perforation, the counting of the encodement pulses of the encoder16 is started (S62). An A/D value supplied to the MRCIN port is read insynchronism with the encodement pulses as the reference data (S63).Then, whether the ENCOUNT value exceeds 32 or not is determined (S64),and the reference data are read until the ENCOUNT value exceeds 32.

Then, the reference value (MRCREF) is found according to the average orintegration of the reference data which are read 32 times. When theframe count number is incremented by one frame at S65, the processreturns to S60 to find a new reference value (MRCREF).

In this embodiment, after detecting the second perforation, the data of32 pulses are read to obtain the reference data within the width of theperforation where the magnetic information is not recorded at all.However, the first perforation may be used instead of the secondperforation. Another condition may be set if the reference data can beobtained in the area with no magnetic information recorded.

The perforation is 2 mm wide as has been explained with reference toFIG. 23. 32 pulses of the encodement pulse are generated while the filmfeeds 1 mm. On completion of reading the reference data of 32 pulses,the reading part of the magnetic head 12 is still within the width ofthe second perforation.

In this embodiment, after amplification of the signal voltage which isgenerated at the ends of the coil of the magnetic head, the smoothingcircuit smoothes the signal voltage. The signal level after smoothing isread to determine whether there is any magnetic recording. However, asdescribed later, another circuit which has no smoothing circuit may beused for determining whether there is any magnetic recording.

FIG. 25 is a block diagram illustrating another embodiment of a circuitwhich determines whether there is any magnetic information recorded ornot. In this embodiment, the signal voltage obtained with the magnetichead 12 is amplified by an amplification circuit 80 and is input to aninput terminal of a comparator 82. The signal from the amplificationcircuit 80 is as the signal which has not been input to the smoothingcircuit 32 in FIG. 4.

A VR value is input to the other input terminal of the comparator 82from a VR value switching circuit 84, and the VR value is a referencefor comparison. The camera CPU 86 switches the VR value so as todistinguish between a part of large amplitude as shown in FIG. 8 and apart of small amplitude in proximity of the center of FIG. 8.

That is, the VR value switching circuit 84 has two ports 1 and 2 asshown in FIG. 26, and it outputs four VR values V₁ -V₄ shown in thefollowing TABLE 2 according to whether the ports 1 and 2 are groundlevel (L) or open (OPEN).

                  TABLE 2                                                         ______________________________________                                        Port 1      Port 2    VR value                                                ______________________________________                                        V.sub.1                                                                             open      open      V.sub.AF                                            V.sub.2                                                                             L (GND)   open      V.sub.AF R.sub.2 /(R.sub.1 + R.sub.2)               V.sub.3                                                                             open      L (GND)   V.sub.AF R.sub.3 /(R.sub.1 + R.sub.3)               V.sub.4                                                                             L (GND)   L (GND)   V.sub.AF R.sub.2 R.sub.3 /(R.sub.1 R.sub.2 +                                  R.sub.1 R.sub.3 + R.sub.2 R.sub.3)                  ______________________________________                                    

If the part of large amplitude shown in FIG. 8 is input to thecomparator 82, the comparator 82 outputs, to the camera CPU 86, a pulsesignal which is synchronous with one of the clock pulse and the datapulse which compose the magnetic information. On receipt of the pulsesignal from the comparator 82 (that is, when there is a change in theinput signal), the camera CPU 86 determines that the frame has alreadybeen exposed. If receiving no pulse signal or an extremely small numberof pulses (the input signal is regarded as noise), the camera CPU 86determines that no magnetic information is recorded in the frame, whichhas not been exposed yet. The camera CPU 86 switches the VR value, whichis output from the VR value switching circuit 84, to an optimum value soas not to change the signal output from the comparator 82 while themagnetic information is not regenerated (only noise is input).

FIG. 27 illustrates the second embodiment of the record regenerationcircuit 15 in FIG. 1. The parts similar to those in the first embodimentdescribed with reference to FIG. 4 are denoted by the same referencenumerals, and they will not be described in detail.

The second embodiment is characterized by a peak hold circuit 132, whichis provided instead of the smoothing circuit 32 and the low-pass filter33 in FIG. 4.

The peak hold circuit 132 comprises an operational amplifier 140, adiode 142, a condenser 144, an analog switch 145 and a MOS FET 148 as abuffer. The output of the peak hold circuit 132 is input to the A/D port(MRCIN) of the camera CPU.

The analog switch 145 is ON/OFF controlled according to the signal (H/L)input from the output port (MRCRESET) of the CPU. By turning on theanalog switch for resetting, the condenser 144 is discharged.

In order to recognize the position of the unexposed frame by means ofthe magnetic information recorded in the magnetic recording layer on thephotographic film 7, whether the magnetic information is recorded or notin the magnetic recording layer is determined. The contents of themagnetic information, that is, "1" and "0" of the binary code do nothave to be read accurately. For this reason, the peak hold circuit 132detects the peak of the signals amplified by the amplification circuit30 for a predetermined period of time, and holds the peak value. Then,the voltage level of the peak of the signals is read from the A/D port.

In this case, the peak hold circuit 132 is reset at regular intervals,and the voltage level is read multiple times for one magnetic recordarea. Whether the magnetic information is recorded or not is determinedbased on the comparison between the average or integrated value and thereference value.

The regenerated signal via the peak hold circuit 132 is input to the A/Dport (MRCIN) of the microcomputer 2. According to the regeneratedsignal, the microcomputer 2 determines whether any magnetic informationis recorded or not.

Description will hereunder be given of the operation during regenerationin the second embodiment of the record regeneration circuit in FIG. 28with reference to waveform charts.

FIG. 28 (a) is a waveform chart showing an example of signals which havejust output from the amplification circuit; FIG. 28 (b) is a waveformchart of the signal output from the MRCRESET port of the microcomputer2; and FIG. 28 (c) is a waveform chart of the signals input to the MRCINport via the peak hold circuit.

As shown in FIG. 28 (a), the signal which has just output from theamplification circuit 30 includes a clock signal which corresponds tothe clock pulse, and a data signal which corresponds to the data pulseinserted into the first or second half of one period of the clock pulseaccording to the record data of "0" or "1". The clock signal is providedat the minus side and the data signal is provided at the plus side if anamplifier ground (2.3 V) is a reference.

If the H level signal is output from the MRCRESET port of themicrocomputer 2, the analog switch 145 in FIG. 27 is turned on, and thepeak hold circuit 132 is reset. When the output from the MRCRESET portbecomes the L level, the peak hold circuit 132 starts detecting theminimum value of the amplifier output is started. On receipt of a signalwhich is smaller than the signal once held, the peak hold circuit 132updates the held value to hold the smaller value as shown in FIG. 28(b).Thus, the peak hold circuit 132 detects and holds the minimum value ofthe amplifier output until the peak hold circuit 132 is reset again. Thevoltage level held by the peak hold circuit just before resetting isread from the A/D port. The peak hold circuit 132 is reset multipletimes within the magnetic record area for one frame, and the voltagelevel is read multiple times.

If the above-mentioned peak hold circuit 132 is used, the calculation ofthe regenerated data (MRCAD) (S51) in FIG. 17 is executed on theprocedure described in FIG. 29.

As shown in FIG. 29, the integrated value of the A/D value (MRCADB) ofMRCIN and the count value (COUNT) for counting the integration areinitialized to "0" (S302). The count value (ENCOUNT) counting theencodement pulses for specifying the reset timing is initialized to "0"(S304), and then MRCRESET port is turned to the high (H) output (S306)to start counting ENCOUNT (S308). If ENCOUNT exceeds 1, MRCRESET portturns to low (L) output (S312).

Then, whether ENCOUNT corresponds to 16 or not is determined (S314), andthe process is looped until ENCOUNT reaches 16. During this period, thatis, for 16 encodement pulses, the peak hold circuit 132 continues todetect the peak (the minimum value).

When ENCOUNT is 16 at S314, the A/D value of MRCIN (MRCINAD) is measured(S316). The measured MRCINAD is added to an integrated value MRCADB soas to calculate a new MRCADB value (S318), and counts up the count ofintegration (COUNT) by 1 (S320).

Then, whether COUNT representing the number of integration correspondsto 16 or not is confirmed at S322, and the above-stated steps from S304to S322 are repeated until COUNT reaches 16. After MRCINAD is measured16 times and the integrated value MRCADB is obtained, MRCADB is dividedby 16 to obtain the regenerated data (MRCAD) (S324).

Then, the process returns to the sub-routine of the MRC control shown inFIG. 17, and proceeds to S52.

The peak hold circuit 132 is reset multiple times (16 times) duringregeneration of one magnetic record area, and the outputs of the peakhold circuit 132 are read multiple times. Then, the average of theoutputs is compared with the reference value. Thus, the determinationerrors resulting from the irregular noise, etc. are prevented, andwhether there any magnetic information is recorded or not can bedetermined accurately.

FIG. 30 shows the third embodiment of the recording and regeneratingcircuit 15 shown in FIG. 1.

In the second embodiment described in FIG. 27, the circuit becomes validif the noise from the motor is generated at one of the plus and minussides. FIG. 30 shows an example of the construction of the recording andregenerating circuit which may be applied to the case when the noise ofwhich polarity is unsettled is generated. Parts similar to those in thesecond embodiment described with reference to FIG. 27 are denoted by thesame reference numerals, and they will not be described in detail.

As shown in FIG. 30, at the rear of the amplification circuit 30, thereare provided in parallel the first peak hold circuit 133 which detectsthe maximum value of the signals and the second peak hold circuit 132which detects the minimum value of the signals. In addition, adifferential amplifier 134 is provided whose differential signals areoutputs from the first and second peak hold circuits. The first peakhold circuit 133 consists of an operational amplifier 180, a diode 182,a condenser 184, an analog switch 185 and a MOS FET 188 as a buffer. Thefirst peak hold circuit 133 is similar to the second peak hold circuit132, and these two circuits are different only in the direction of thediode 182 and that the MOS FET 148 is a p-channel device and the MOS FET188 is an n-channel device. The signals from the first peak hold circuit133 are input to an inverting input terminal of the differentialamplifier 134, and the signals from the second peak hold circuit 132 areinput to a non-inverting input terminal of the differential amplifier134. The differential amplifier output is output to the MRCIN port.

FIG. 31(a) is a waveform chart showing an example of the signals whichhave just output from the amplification circuit 30; FIG. 31(b) is awaveform chart of a signal output from the MRCRESET port of themicrocomputer 2; FIG. 31(c) is a waveform chart of signals output fromthe first peak hold circuit 133; FIG. 31(d) is a waveform chart ofsignals output from the second peak hold circuit 132; and FIG. 31(e) isa waveform chart of signals output from the differential amplifier 134(gain 1) whose differential signals are shown in FIGS. 31(c) and 31(d).

The reading timing and the processing method are similar to those in thesecond embodiment, and they will not be described in detail.

As set forth hereinabove, according to the present invention, the numberof turns of the coil in the regenerating magnetic head is small in orderto make the magnetic head compact and low-priced. Since the number ofturns of the coil is small, the magnetic head may be used in order torecord the magnetic information. Moreover, the voltage level can becorrectly read, and whether there is any magnetic information or not canbe accurately determined. Since the noise resulting from a change in thefilm feed speed can be eliminated, the voltage level can be readcorrectly. Further, the noise can be prevented from coming into theregenerating circuit from the recording circuit during regenerating.After recording of the last magnetic information, the electric chargewhich is accumulated in proximity of the magnetic head is discharged,and then the non-magnetized area can be formed without fail, therebypreventing the recording errors caused by the oscillating current.

According to the present invention, the reference voltage is cut offfrom the amplification circuit and the driving power is supplied to theamplification circuit during recording, so that the amplificationcircuit can function as the comparator. Thus, even if the signal voltageis input to the amplification circuit during recording, theamplification circuit is not broken. For this reason, there is no needto provide a changeover switch for alternately connecting the recordingcircuit and the amplification circuit with respect to the coil, and anexpensive protection circuit at the input stage of the amplificationcircuit, and therefore, the camera can be low-priced. In addition, theregenerated current flowing through the coil can be directly input tothe amplification circuit, thereby obtaining the regenerated signal withlow noise.

Furthermore, according to the present invention, the preparations forphotographing can be made properly for the partial cartridge, whichcontains the photographic film with one or more of exposed frames andone or more of unexposed frames. If the preparations cannot be madeproperly, the photographing using the partial cartridge is prohibited inorder to prevent a trouble such as double exposure.

It should be understood, however, that there is no intention to limitthe invention to the specific forms disclosed, but on the contrary, theinvention is to cover all modifications, alternate constructions andequivalents falling within the spirit and scope of the invention asexpressed in the appended claims.

What is claimed is:
 1. A camera which determines whether a filmcartridge loaded in said camera is a partial cartridge, containingphotographic film having an exposed frame and an unexposed frame, ornot, and feeds the photographic film from the loaded film cartridge upto a first unexposed frame if determining that the loaded film cartridgeis the partial cartridge; said camera comprising:first battery checkingmeans comprising first determination means for determining whethervoltage of a battery in said camera is more than a first thresholdlevel, and first prohibiting means for prohibiting photographing if theloaded film cartridge is not determined as being the partial cartridgeand said first determination means determines that the voltage of saidbattery is less than the first threshold level; and second batterychecking means comprising second determination means for determiningwhether the voltage of said battery is more than a second thresholdlevel higher than the first threshold level, and second prohibitingmeans for prohibiting photographing if the loaded film cartridge isdetermined as being the partial cartridge and said second determinationmeans determines that the voltage of said battery is less than thesecond threshold level.
 2. The camera as defined in claim 1, wherein thefirst threshold level is voltage level which enables properphotographing and one-frame feeding after photographing of said camera.3. The camera as defined in claim 1, wherein the second threshold levelis voltage level which enables film feeding for correctly detecting theunexposed frame on the photographic film from the loaded film cartridge.4. A camera which detects whether or not a film cartridge loaded in saidcamera is a partial cartridge, containing photographic film having anexposed frame and an unexposed frame, and feeds the photographic filmfrom the loaded film cartridge up to a first unexposed frame ifdetermining that the loaded film cartridge is the partial cartridge,said camera comprising:a battery checking section comprising amicroprocessor operative to compare a voltage of a camera battery to oneof either a first predetermined threshold level when the partialcartridge is not detected, or a second predetermined threshold levelwhen the partial cartridge is detected, wherein said secondpredetermined threshold level is greater than said first predeterminedthreshold level, said battery checking section outputting a signalindicative of the comparison made by said microprocessor; and aphotograph prohibiting section operative to prohibit the camera fromtaking a photograph based on the signal output by said battery checkingsection when; (a) the voltage of the camera battery is less than saidfirst predetermined threshold level; and (b) the voltage of the camerabattery is less than said second predetermined threshold level.
 5. Thecamera according to claim 4, wherein the first threshold level is avoltage level which enables proper photographing and one-frame feedingafter photographing.
 6. The camera according to claim 4, wherein thesecond threshold level is a voltage level which enables film feeding forcorrectly detecting the unexposed frame of the photographic film in thepartial cartridge.